My XM S1 1993 2.1 TD with a CAV-Rotodiesel mechanical diesel pump has recently began to go on full speed on its self. It has happened three or four times now, shortly after start. After 10 to 20 sec´s with a lot of smoke, the situation is again normalized, and the engine runs smoth and well.
I suspect it to be caused by air in the pump, but would like to hear if others have experienced anything similar.

Kind regards
Jens

If it happens soon after you have started when the engine is still fairly cold, yes its probably air ingress. If you havn't changed the fuel filter lately it could be impeding the flow of fuel causing it to suck air, or it could be the primer diaphram (if its got one) leaking or a leak on any of the connections, including, I belive on a CAV system, the injector leak off pipes.

If it happens when the engine is hot, it could be running on crank case oil vapour, due to a worn engine.

Peter.N.

I experienced this on my 1.7 TZD BX. I'm led to believe the engine is runing on crankcase oil mist due to a worn out engine (mine had done nearly 200,000). It always lasted only a few seconds and always from cold. I have read stories of this happening on other vehicles whereby the engine cannot be shut off as it is burning up all the oil from the sump! 'Best to stand well clear if this problem lasts more than a few seconds as the engine will probably self destruct.

I've never known one actually blow up but it can be pretty scary. You can tell if thats the problem because as the previous post says, you turn the key off and the engine keeps going.

Peter.N.

I spoke to a Lucas specialist, and he told me, that this was caused by air in the fuel. I then put in short pieces of tranlicent hose in the fuel line and traced the air inlet to the fuel filter. Changed the O-ring on the centre bolt and the O-ring on the Water in fuel detector. No air bubbles now, and the problem was solved.

Kind regards
Jens